Circuit interrupter



April 3, 1934. F. KESSELRING CIRCUIT INTERRUPTER Filed Nov. 17, 1950 3 Sheets-Sheet l INVENTOR Frz'zz Kesselrmg.

'ATTORNEY April 3, 1934. F. KESSELRING CIRCUIT INTERRUPTER Filed Nov. 17, 1930 3 Sheets-Sheet 5 Fly. 6.

INVENTOR Frz'zz KesseZrzrzg.

r o I ATTORNEY WITNESS W Patented Apr. 3, 1934 omoorr INTERRUPTER Fritz Kesselring,

Berlin-Hermsdorf,

Germany,

assignor to Westinghouse Electric and Mannfacturing Company, a corporation of Pennsyl- Vania Application November 17, 1930, Serial No. 496,218 In Germany November 19, 1929 12 Claims.

My invention relates to circuit interrupters and particularly to circuit interrupters of the high-voltage type.

In my copending application, Serial No.

461,325 filed June 16, 1930 and assigned to the assignee of the present invention, I disclose a circuit interrupter which effects are extinguishment through the employment of a medium in the vicinity of the are path which freely 1iberates a gas in the presence of an arc. The gas is confined until a predetermined pressure is produced or until a member is moved a predetermined distance, after which the gas is rapidly expanded. The expansion of the gas occurs during the time the current in the system is passing through zero in the course of its alternating cycle and, during'this time, the arc is extinguished. The reason for the extinguishment of the arc and the subsequent prevention of arc reinitiation will be clearly set forth hereinafter;

My present invention embodies improvements in and modifications of the circuit interrupter set forth in the above mentioned copending application which has, for an object, the employment of a. material, adjacent to the arc path, that readily evolves a gas in the presence of an arc and that deposits, through expansion and condensation, or otherwise, solid particles within the arc stream.

Another object of my invention is to provide a bridging member for a pair of arc-drawingand-extinguishing devices that shall combine a movement of rotation with one of translation to efiect a maximum protection against flashovers between the devices because of adverse weather conditions or other causes of a reduced dielectric strength in the atmosphere.

A further object of, my invention is to provide a device for raising the temperature of the fluid employed in the extinguishing structure of the above described type without the danger of lowering the dielectric properties of the extinguishing structure.

A still further object of my invention is to provide a device, which effects extinguishment of an arc owing to a sudden expansion of a gas, with means for controlling the expansion of the gas in accordance with the amount of current flowing in the circuit and the amount of pressure developed by the gas.

A still further object of my invention is the provision of means so associated with an extinguishing device of the above mentioned type that the rate of rise of voltage across the arc terminals, after arc extinguishment, is reduced to furshould be referred to for a better understanding of my invention, in conjunction with the accompanying drawings, wherein:

Figure 1 is a view, partly in section and partly in elevation, of a circuit interrupter embodying my invention,

Fig. 2 is a curve illustrating the relation between the current of the system and the electric tension existing between the electrodes at the time of arc extinguishment.

Fig. 3 is a diagrammatical View of a pair of electrodes illustrating the ionized path existing therebetween at the time of arc extinguishment.

l is an enlarged view, in sectional elevation, of my arc-extin uishing device which is a slight modification of that illustrated in Fig. 1.

5 is a curve disclosing the relation existing between the expansion of the gas and the current change in the course of its alternating cycle.

Fig. 6 is a curve disclosing the relation existing between the temperature and the pressure of the vapor within the arc-extinguishing device, and

Figs. '7, 8 and 9 are views, in sectional elevation, illustrating modified forms which my arcextinguishing device, shown in Fig. 1, may assume.

Referring to Fig. 1, my invention comprises, in general, a pair of stationary contact members 1 mounted on insulating pillars 2 and conductiveiy connected by a bridging member 3. An operating mechanism 4 is associated with the bridging member 3 for effecting its engagement with or disengagei. ent from the contact member 1. When the mechanism 4 is actuated to move the bridging member 3 away from the contact members 1, arcs will be established in series relation to each other in arc extinguishing devices 5 which are associated with each contact electrodes, ions and electrons, charge carriers, move in the electric field carry the current between the electrodes. Alternating current passes through zero-current value during each half cycle. At this instant, there are present in the space between the electrodes, carriers of electric charges, the motions of which are not directed or guided. As a rule, the electric field between the electrodes is built up when the voltage again increases and the charge carriers are thereby set in motion to provide a conducting path through which the current again flows.

Since the mass of the ions and the electrons is extraordinary minute, a high velocity will be imparted to them by very small electrical fields. Up to the present time, it has been thought necessary to have a marked reduction in the intensity of the electric field to interrupt the current, hence, a great velocity and a wide separation of the electrodes were deemed necessary to extinguish the are.

This invention consists in extinguishing the are by allowing finely divided. liquid or solid materials to attach themselves to the electrified particles, to the free electrons in particular, which are present in the arc, while the current is passing through a zero point in its cycle Wave.

This attaching of material particles occurs because of the fact that the electrons have a tendency to attract any such particles in their vicinity.

Even the most minute material particles are one thousand to one million times as large as the current-carrying electrons. When the cur- ..,rent increases after passing through zero value,

the electrical field acts on the charged particles, which consist of the electrons with the material particles attached. The mass of these conglomerates is, as has been suggested, from a thousand to a million times greater than that of the electrons before taking on the particles, and their acceleration is correspondingly less, since the intensity of the electrical field depends on the voltage of the circuit and is not changed by the addition of material particles to the elec-- .liquid material collect around each free electron. In the case of many materials, water, for instance, the attaching of a single molecule to each electron is sufiicient to produce the desired eifect. Each electron, with its attached molecule or group of molecules, forms a negative ion having a large mass.

Referring to Figs. 2 and 3, contacts 1 and 6 represent the electrodes between which the arc is established. The current I is represented in Fig. 2 as it passes through zero at the point P.

Electrically charged particles 7 are to be found between the electrodes 1 and 6. An electric tension, corresponding to the curve 6, develops between the electrodes 1 and 6 at the moment when the current passes through zero. This tension generates an intensity of electric field E which acts on each of the particles '7 and accelerates them. This acceleration b is expressed by the equation where E is the intensity of field at the particular instant; q, the elementary charge of the electrically charged particles; and m, the mass of one of these particles. If now, material particles are attached to one of these electrically charged particles, by the method to be described later, the total mass of the conglomerate will be M :m-tm. Here m represents the mass of the attached particles. The charge on the entire mass remains equal to q. The acceleration now is l q l'g lv l Since m may be as much as 1 million times greater than m, the acceleration b will be only about the millionth part of b, hence, the movement of the particles is negligible. This is equivalent to current interruption.

The material Which can attach itself to the electron may be a solid material like dust or soot. Water is a particularly suitable liquid material.

The condition required for the extinction of the arc, is that particles, capable of attaching themselves to the electrons, must be present in the space between the electrodes at the instant when the current passes through zero. This condition will be particularly well fulfilled if, according to the invention, a gas or a vapor is brought into the space between the electrodes which, on 0001- Acetylene, for instance, separates soot when cooled, and water condenses from steam. Saturated steam is particularly suitable but the acetylene is highly desirable because of its ability to deposit solid particles within the arc stream. Such solid particles not only reduce the acceleration of the ions but also constitute centers upon which the charged ions liberate their charges and become further non-conductive.

This process of bringing gas or steam into the arcing space has a great advantage because of the expansion property of gases and vapors, by which every space may be completely filled. Therefore, the space between the electrodes will, at all times, contain a sufficient amount of unused vapor or gas to replace that which has been decomposed inthe arc, and there will always be enough particles capable of attaching themselves to the electrons in the path of the are at the instant when the current passes through zero. This action, resulting from the natural expansion of the gases in a closed space surrounding the electrodes, may be aided by producing an artificial flow of gas through the path of the arc, by allowing the gas to flow out of the vessel enclosing the electrodes in such manner as will be explained fully hereinafter. The cooling required for separating the solid or liquid particles from the gas or vapor may be attained either by allowing the gas or vapor to do external work, as in adiabatic expansion, or by removing the heat by conduction. The vapor or gas form material is preferably generated from a liquid or a solid by the heat of the arc although it is to be understood that the vapor may be supplied from some other source.

Since the arc can be extinguished by the attaching of material to the electrons only during the passage of the current through zero and there are no simple means of bringing the material between the electrodes at that instant, it is necessary that the conditions for attaching the particles shall extend over a period of time greater than one-haif cycle of the alternating current to be interrupted.

In order that this condition shall exist during the entire half cycle, a continuous supply of fresh material must be furnished to the path of the arc during this time. If condensable gases or vapors are employed for quenching the arc in an enclosed vessel containing the electrodes, an amount thereof sufficient to fulfill the above conditions, must be introduced or generated in the vessel before each arc extnction. Means for cooling the gaseous material or vapor must, of course, also be provided so that the solid or liquid particles shall be continuously deposited in the are stream over a period of time greater than one-ha1f cycle.

To extinguish an arc according to the method described above, it is, therefore, unnecessary to introduce an insulating medium between the electrodes and the charged particles, and the oil, which has been so generally used as a dielectric for this purpose, may be omitted. With the removal of the oil, from which the action of the are produces highly explosive gases, when mixed with air, a source of danger is removed which had to be particularly considered, heretofore, in the construction of circuit interrupters.

Other materials, which may be employed besides acetylene and water and which are non-inflammable and possess high dielectric properties, are triarylphosphate, tricresylphosphate, trichlorethylene, pentachlorethane and carbon tetrachloride,

a possibility that creepage paths will be established, and these can be avoided by the employment of insulating fluids, such as those indicated above. The amount of fluid required for the expansion breaker is much less than that required for the well known oil-immersed circuit interrupter and, for this reason, the cost of the fluid does not enter, to a great extent, in its selection.

The circuit-interrupting structure shown in Fig. 1, is intended, primarily, for outdoor use and, for this reason, the conducting members are ported on high-pillar insulators. A mechanism is provided to operate the cross bar which is connected to insulating means in order that the dielectric to ground through the central column shall not be lowered. The structure herein shown consists of pistons in cylinders which are joined together by insulating and metal pipes containing a fluid for effecting the operation of the bridging member.

' It is to be understood that my invention is not limited to the fluid-contained operating mechanism but that mechanical levers and bell-cranks, provided with a suitable actuating device, well lrnown in the art, may be substituted therefor. In order to increase the creepage distance over the contact members and the bridging members, when separated, I rotate the latter member ap proximately to thereby increase the breakdown path between the contact members and the bridging bar.

As pointed out above, in regard to Fig. 1, the pillar insulators 2 have arc-extinguishing chambers 5 mounted about the contact members 1. These contact members are provided with terminal lugs 8, mounted outside of the extinguishing chambers 5 to facilitate the connection of the circuit interrupter in a circuit. Between the insulators 2, I provide a pillar insulator 9, the hollow interior of which has insulating tubes 11 and 12 located therein for the purpose of conducting a pressure medium, such as compressed air or an insulating fluid, to the spaces in an operating cylinder 13 below and above the piston 14, respectively. The pressure medium is conducted outside of the insulator 9 by means of metal tubes 15, 16 and 17. The tubes 16 and 1'7 are connected, respectively, to the spaces on either side of a double-acting piston 18 of a control cylinder 19.

A piston rod 21 is mounted on the piston 14 and supports the conducting bridging member 3 and, when actuated, causes the engagement of the contact rods 6 with the fixed contact members 1 when the breaker is operated to closed-circuit position. When the piston 18, of the control cylinder 191s again moved from one limiting position to another, the piston 1 1 is moved into its upper position, the bridging bar 3 is moved upwardly therewith and the engagement between the fixed and movable contact members 1 and 6, respectively, is interrupted.

During this upward movement, the contact rods 6 are moved out of the switch chamber 5, and the bridging member 3 is rotated as a projection 22 on the piston rod 2]. slides in a helical groove 24; in the inner wall of the cylinder 13. The reverse movement of piston 18 will affect a downward movement of the piston 14; and produce a counter-turning and lowering of the bridging member 3 until the contact rods 6 engage the contact member 1 to again establish the electrical circuit.

Referring to Fig. 4, the extinguishing device 5 is provided with means for raising the temperature of the fluid and for effecting expansion over a period greater than one half cycle. The chamher is provided with a base 25 made of copper or other good conducting material associated with metal side walls 26. A heat-insulating material 20 is provided on the outside surface of the wall 26 to prevent the escape of heat, transferred therewithin.

In order to prevent a lowering of the dielectric property within the extinguishing device 5, I have provided the heating unit in an associated chamber 27 of a porcelain cylinder 28 upon which the extinguishing device 5 is mounted. A base 29 is attached to the bottom of the porcelain cylinder 28, in such manner as to constitute a liqind-tight connection therewith. A bushing 31 extends through the end of the cylinder 27 and insulates a main current-carrying conductor 32 from a liquid 33 enclosed within the cylinder 28. A grounded flange 34- is mounted on the bushing 31, and a winding 35 is supported on the flange.

An alternating current is conducted to the coil by means of terminals 36 and conductors 37. When a current is thus supplied to the coil 35, eddy-current losses occur in the conductor 32, causing the conductor to become heated. The heat thus generated within the copper conductor 32 is readily transferred to the base 25 and, therefore, to a liquid 38 provided within the casing 26. By this means, the liquid 38 is prevented from freezing when the circuit interrupter is in open position and, when in closed position, the additional heat supplied by the current flowing in the conductor raises the temperature of the liquid and decreases the amount of energy absorbed from the are before the temperature of the fluid is raised to the vaporizing point.

, passed in such manner as to be isolated from the arc-extinguishing chamber. The novelty of this construction is the provision of a heating device for the liquid of an arc-extinguishing chamber which is completely isolated from the main conducting members.

In order to provide a uniform expansion of the gas and to have the gas move at right angles to the movement of the current through the arc, I provide an outlet ll in the side wall of the casing 26 above the level of the liquid 38. A valve 42 is provided in the outlet of the casing and is biased by a spring 43 to closed position by the pressure exerted between the arm 44 and the valve. Since the contact rod 6 fits snugly within th opening 145 in the casing 26, practically no gas escapes from this opening.

When an arc is established between the contact members 1 and 6, a portion of the liquid 38 in contact therewith will vaporize, and a pressure will be developed within the casing 26. When this pressure reaches a predetermined value, the valve 42 is opened, and a portion of the gas escapes. The expansion of the remaining portion of the vapor takes place at right angles to the arc stream and, because of this cross-flow, the arc stream is completely saturated with the gas. As the vapor suddenly expands, it condenses, that is, changes from the superheated to the saturated vapor state, and produces immobile particles which are attracted by the ions of the arc path,

as set forth above, to effect a non-conducting path between the contact members.

The tension of the spring 43 should be made such that the expansion will continue for a period greater than one-half cycle of alternating current to be interrupted. Further, it is necessary, in order that a suilicient amount of condensate shall always be present to extinguish the are, that the critical pressure ratio should not decrease below a predetermined amount, determined by the proper dimensioning oi the gas space of the extinguishing chamber 26 and the outlet ll thereof.

The worst possible condition that could occur for effecting the quick extinguishinent or" the arc, is that present when the expansion begins at the time the current is passing through zero. Upon such an occurrence the resulting condensation is not rapid enough to be effective during the current zero and, for this reason, the

condensation must continue until the current again passes through zero value in the course of its cycle wave. Referring to Fig. 5, the time between the occurrence of two zero points of the cycle wave is represented by and it is therefore apparent that the expansion must continue over a time equal to approximately in order that the arc shall be extinguished in accordance with the method above described.

A measure for the rapidity of elimination of the electrons between the contacts 1 and 6 is to be found in the amount of condensate which is available at the instant the current passes through zero and this will vary with the amount of gas flowing out of the outlet opening 41.

In the case of a gas of constant volume flowing out of the chamber 26 and having a pressure P at the beginning of the outflow, the amount of escaping gas will be much slower with decreasing pressure P, up to the critical pressure ratio, than after the pressure has decreased below this ratio. The critical pressure ratio is reached in the instant when the pressure at the outlet 41 equals the pressure existing in the chamber into which the gas flows or to atmospheric pressure if it flows directly into the air.

This discloses that the chamber 26 should be filled, at the beginning of the expansion, with a volume of gas, proportional to the energy to be interrupted, having such pressure that, at the end of the expansion time the pressure within the casing 26 shall not have dropped below the critical pressure ratio. When this proportion is maintained, a suihcient amount of condensate for extinguishing the arc will al ways be available after the second passage of the current through Zero value.

This same ratio holds for circuit interrupters which are operated at greater capacities than that for which they are normally rated. A greater pressure is generated within the chamber because of the greater volume of gas liberated by the heavier current arc, which may thereafter be reduced to the amount determined by critical pressure ratio in the necessary expansion time by increasing the outlet opening. A large drop in pressure ensues because of the increased flow of gas during this time and a greater amount of condensate, necessary for the successful extinguishment oi the arc of greater intensity, will be generated.

Fig. 5 discloses a curve in which the expansion time is shown as the abscissee and the value of the outfiowing gas per square centimeter of outlet opening is represented as the ordinate, in accordance with the equation g flt), in which 9 indicates the amount of gas per square centimeter of outlet opening which escapes in the time dt. By integrating this curve between the limits of 13:0 and the amount of gas per square centimeter of outlet opening during the entire time will be obtained.

The volume of the gas space in the extinguishing chamber has been assumed as being as large as is necessary for obtaining an initial pressure P with an amount oi gas developed by the are for switches of normal capacity. If, from this volume of gas, present at the beginning of the expansion, the amount of gas is subtracted which is still present in the gas space at the end of the expansion time upon reaching the critical pressure ratio and, if I divide the difference of these two volumes by the amount of gas which flowed out per sq. centimeter of cross section of the outlet during the expansion time a value is obtained for the size of the outlet opening in square centimeters.

Another device which I have successfully employed to produce the proper amount of condensate at the time the current is passing through ;the zero value of its cycle wave is disclosed in Fig. 7. The contact member 1 is mounted in the bottom of a chamber 46 which is open at the top. The liquid 38 is contained in the lower half of the casing, and an electromagnet 4? is immersed in the liquid, having its legs 48 extending slightly thereabove. A freely movable piston 49 rests upon the legs 48 slightly above the liquid 38 to therewith constitute a small chamber. The piston is made of magnetic material and is attracted and held by the magnet 47, when energized, against the pressure developed above the liquid.

' The movable contact member 6 extends through 1 the piston 49 and through the hollow tube 51 which is carried by the piston to limit movement of its upward path and to prevent it from being forced completely out of the chamber 46. This limiting motion is effected by the engagement of the member 51 with a conducting collar 52 mounted on the conductor member 6. A main circuit 53 is wound about the legs 48 of the magnet 47 and is connected to the conducting collar 52.

When the contact members 1 and 6 are in closed position, the piston 49 is held firmly against the magnet 47, and only a slight area is present between the surface of the piston 49 and the liquid 38. As the contact members are separated, the continued energization of the circuit 53, through the arc established between the contact members, causes the piston 49 to be retained by the arm 48 against the pressure built up by the accumulated vapor in the presence of the arc. The pressure will continue to build up until such value is reached, with respect to the current in the circuit 53, as it approaches zero value, that the piston 49 will be forcibly released from the magnet 47, and rapid expansion of the gas will ensue. This relation of pressure to the holding force of the magnet is balanced in such manner that the preponderance of pressure over the force of the magnet will always occur sometime before the current reaches zero value. In this construction, the expansion and condensation will take place before and during the time that the current is passing through its zero value, and the arc will thereby be always extinguished.

The arc-extinguishing chambers heretofore referred to, are dependent for their successful operation upon the employment of fluids which condense upon expansion and which will be chemically disassociated as little as possible at high temperatures, in order that they may be reconj densed and repeatedly employed. Directly opposite these types of fluids and the expansion chambers. heretofore referred to, are the fluids which liberate vapors which condense during the compression rather than during the expansion of the vapor, such as ether, chloroform, and the like.

The operation of the extinguishing device is reversed when employing such liquids, since the volume of the vapor space is reduced instead of increased to affect condensation. The extinguishing device disclosed in Fig. '7 readily adapts itself to employment with such liquids. In this construction, the magnet 47 is placed above the piston, which is thereby held near the top of the chamber 46 against the pressure of a spring (not shown). a suitable means which is actuated by the developed pressure within the casing 46 or by the upward movement of the contact members 6 after which, as the current in the circuit 53 approaches zero value, the bias of the spring overcomes the force of the magnet 47, and the vapors are thereby compressed to effect the desired condensation.

In order to prevent the reinitiation of an are after extinguishment, the conductivity of the arc path must be dissipated with such rapidity that the rate of rise of voltage du, across the contact members 1 and 6 will not be suificient to cause arc reinitiation. One method for effecting this condition is to assure that a predetermined drop in temperature of the vapor occurs. The relation between the impressed voltage and the temperature drop is expressed by the equationdT du 25 K3 in which, K is a constant for the fluid employed and depends mainly on the physical characteristics of the fluid rather than on the initial pressure of its vapor in the extinguishing chambers. This condition is met by the adiabatic expansion of the vapor in the region in which changes of pressure correspond to large changes in temperature. This change in temperature dT depends mainly on the external work done by the vapors, that is to say, on the change in pressure and volume.

In Fig. 6, the curve illustrates the relation between the temperature T and the pressure P, the vertical axis representing temperatures while the horizontal axis represents pressures. The curve was plotted from data obtained when employing water vapor, the point K representing the critical point thereof having a temperature of 374 and a pressure of 224.2 atmospheres.

According to the curve, the change is small in the presence of high pressures but is large for low pressures. If

E d t expresses the pressure drop at the beginning of the expansion and this pressure drop is assumed to be constant, that is to say, independent of the initial pressure, it was determined, in order to obtain a large relation or to successfully operate with the least possible dp with a predetermined dT, that the expansion will occur in that region of the saturated or wet vapor in which,

er p

is large, that is to say, in region of low pressures. In this construction, the arc can be successfully extinguished and prevented from reigniting when a small drop of pressure occurs in the extinguishing device. A proper dimensioning of the steam chamber and of the cross section of the outlet thereof will effect the required amount of temperature drop.

The spring is retained by To properly extinguish the arc, the pressure drop Q dt and, therefore, the extinguishing action or the device to a large degree. If, on the other hand, the expansion chamber is subjected to arcs of large current value, the initial pressure of the vapor will be so large that the extinguishing chamber may become injured.

To meet this condition, I have provided a large opening 54 in the extinguishing chamber 55, as shown in Fig. 8, and have provided a valve 56 in the opening 54 which completely closes the opening when the circuit interrupter is in closed position. The valve 56 is in the nature of a shutter, similar to the iris type of shutter to be found on a camera, which completely closes the opening when low-current arcs, which develop low pressures, established between the contact memhere. When heavy-current arcs are present between the members, the disc is completely opened, and harmful pressures are thus avoided.

Magnetic means may be provided for controlling the movement of shutter 56 or mechanical actuating means, responsive to pressure or to contact movement may be employed. Either the mechanical or magnetic controlling means will operate the shutter to assure that the maximum pressure required for are extinguishment will be present for arcs of all current values and that the pressure exceeding this maximum amount will be liberated before the expansion producing the condensation occurs.

Another method of assuring that the conducting path between the electrodes is sufliciently dissipated in relation to the rate of rise of impressed voltage thereacross is that effected by increasing the time for this dissipation by slowing up the rate of rise of the impressed voltage across the contact members. This slowing up of the rise of voltage is accomplished by employing an impedance, such an ohmic resistor, an inductance or a capacitance connected in parallel with the contact terminals.

In Fig. 8, I disclose such an impedance 5'? in shunt relation to the contact member 1 and a conducting partition 58 which is disposed parallel to the base of the chamber below the level of the liquid 38. A hole 59 is provided in the partition 58 through which the movable contact member 6 extends to complete a circuit with the contact memher 1.

The rate of rise of voltage across the contact members i and 6 is determined by the inherent number of oscillations 2Tr- /eL of the disconnected system, that is to say, by its capacity C and by its inductance L. The connection of the impedance, as disclosed in the struccillations of that part of the system which deter mines the voltage increase to thereby reduce the number of oscillations which efiects a reduction in the rate of rise or the impressed voltage.

After the contact member 6 has been separated, a current will iiow through the impedance 57, in parallel relation to the arc, which will be initially very small because of the small voltage at the arc.

s soon as the movable contact member 6 passes out of the opening 59 in the partition 58, the vapor which has been accumulating in the lower chamber will expand through the opening 59, and a large portion thereof will be condensed in the path of the arc, and are extinguishment will ensue before the rise of voltage across the contacts becomes sufiicient to cause arc reinitiation.

In the presence of the impedance 57, the rate of rise of voltage is retarded, thereby increasing the time within which the condensate will be able to operate on the ions to further decrease the conductivity of the arc path. This delay in the rate of rise of voltage enables my circuit interrupter to operate to interrupt greater loads in accordance with the above formula. This construction ensures successful operation of the circuit interrupter with a smaller temperature drop l in the ease of adiabatic expansion, with a smaller amount of expansion or a smaller pressure drop.

If the arc is extinguished in the space below the partition 58, a current will then flow between the contact 1, the impedance 57, the partition 56 and the movable contact member 6, the amount of this current being determined by the value of the impedance 57. This small current may be easily interrupted if the impedance 5'? has a sufficiently high ohmic resistance. This small current is almost in phase with the current in the circuit and will be quickly interrupted in the upper part or" the chamber the next time the current or the system passes through zero value.

The beneficial results eflfected by the impedance, as set forth above, may be considerably increased by providing a plurality of parallelconn cted impedances to subdivide the switching operation into a plurality of related steps. These related steps may be of the same value, that is to say, having the partitions equally spaced and shunted by impedances of equal value, or they may be varied by alternately employing larger and smaller spacings for the partitions and shunting them by impedances having different values.

In Fig. 9, I disclose a structure wherein the separate impedance 57 is eliminated by utilizing the resistance or" the fluid as a means for decreasing the rate of rise of the impressed voltage. As an example of such construction, in case wat is employed as the extinguishing fluid, a sufficient amount of soda may be added to obtain the required resistance. The length of time. such resistance is in circuit between the contact members is regulated by the height of the fluid over the stationary contact member 1, located at the bottom of the extinguishing chamber.

When the wall of the chamber 55 is made of conducting material, an insulating tube 61 is provided about the contact 1 which extends upwardly above the liquid. This tube insulates the path through the liquid from the contact memher 6 and the arc to the wall of the chamber 55. The length of the path of resistance will depend upon the height of the fluid above the contact member 1.

Small openings 62 are provided in the bottom of the tube 61 to equalize the height or" the liquid within and without the tube. These openings, being below the contact member 1, provide a greater length of resistance path for the cubrent to the bottom or side walls than that directly to the contact member, and, for this reason, does not affect the main resistance path of the cur rent.

It will be seen that, after an arc has been extinguished in the manner hereinabove set forth, that the presence of the body of liquid above the contact 1, offers resistance to the how of current and operates in the same manner as the impedance 5'? heretofore referred to in relation to Fig. 8. In both constructions, the rate of rise of voltage is considerably reduced to thereby increase the time available for deleting the conductivity of the path between the contact members.

When an arc is established in a fluid of an arc extinguishing chamber similar to those hereinbefore referred to, it is necessary, in order to obtain the required amount of superheated vapor and the resulting pressure, to have the fluid in continuous contact with the are so that the temperature of the fluid may be quickly raised to its volatilizing point. It is further necessary to provide an outlet for the vapor which will be located in such position that the fluid, agitated by the sudden expansion, will not be carried to the opening to clog it and to thereby prevent the rapid liberation of the vapor.

Referring to Fig. 9, I have provided an outlet duct 68 which is in direct communication with the base of the contact 1 upon which the arc impinges. At this point, the fluid will be quickly changed to a vapor or bodily moved from the area about the contact member. When the expansion occurs, the vapors will rush out of the duct 68 without any danger of the fluid being carried into the opening, since the presence of the arc prevents the fluid from passing into the hollow portion of the contact member. The resulting flow of vapor through the duct 68 reduces the size of the vapor bubble about the arc, and the fluid is permitted to more intimately engage the arc stream to thereby liberate more fluid until such time as the arc is completely extinguished.

It will thus be seen that I have provided a circuit interrupter of the high-voltage type wherein the arc extinguishment takes place in a very short time. in the nature of one-half cycle of alternating current. The interruption occurs because of the rapid expansion of a vapor which was trapped duing the establishment of the arc and which provides a condensate or saturated vapor in the arc path during the time the current is passing through zero in the course of its cycle wave. This condensate may include liquid particles or particles that are solid, which attach Ithemselves to the charged ions to thereby decrease their mobility to such point that they become non-conductors. The condensate has been specified as being precipitated by the rapid expansion of l the vapor, and it is to be under- 1 stood that any change to produce the condensation of a vapor is within the contemplation of my invention, when the word expansion is employed. For example, ether, chloroform, or similar fluids liberate a vapor which condenses on the application of pressure as set forth hereinabove.

While I have described and illustrated several embodiments of my invention, it will be apparent to those skilled in the art that many changes, omissions, additions and substitutions may be made in the structure herein described and illustrated without departing from the spirit and scope of my invention, as set forth in the accompanying claims.

I claim as my invention:

1. The combination, in a circuit interrupter of a pair of relatively movable contact members for opening and closing the circuit, a pressure chamber for enclosing said contact members during the opening of the connected circuit, a vaporevolving iiuid within said chamber adjacent to the path of movement of said relatively movable contact members, a movable partition within said chamber for regulating the volume thereof, and magnetic means responsive to the current in the circuit to be interrupted for retaining said partition in a predetermined position during each operation of the interrupter until the pressure of the accumulated vapor resulting from the action of the arc exerts a greater force on the partition than that exerted by the magnetic means, the release of said partition causing an expansion of the entrapped gas which expansion results in the surrounding of the arc with are extinguishing fluid in the vapor state.

2. In a circuit interrupter, a closed pressure chamber, means for establishing an are within said chamber, a vaporizable liquid within and only partially filling said chamber, said liquid and the gas evolved therefrom by the action of the are being retained in said closed chamber at substantially constant volume, and releasable pressure maintaining means acting, in response to the pressure within said chamber, during each operation of the interrupter to release the pressure within said chamber and thereby produce a change of state from the superheated to the saturated vapor condition in the fluid surrounding the arc, said chamber and said pressure maintaining means being so proportioned that the change of state resulting from the release of the pressure within said chamber is caused to persist for a sufiicient period of time to include at least one zero point in the arc current.

3. In an alternating current circuit interrupter, a pressure chamber, means for establishing an are within said chamber, a vaporizable liquid within and only partially filling said chamber, and a releasable means for maintaining pressure within said chamber, said pressure maintaining means acting at a predetermined pressure during each operation of the interrupter to release the fluid entrapped within said chamber and thereby cause that part of said fluid remaining within chamber to change fromthe superheated to the saturated vapor state, said chamber and said pressure maintaining means being so proportioned that the cooling resulting from the pressure releasing operation causes the entrapped iiuid adjacent the arc path to remain in the saturated vapor state for an interval of time at least equal to one alternation of the arc current.

4. In a circuit interrupter, a pressure chamber, means for establishing an are within said chamber, a vaporizable liquid within and partially filling said chamber, and a releasable means biased to the closed position for maintaining pressure within said chamber, said pressure maintaining means acting at a predetermined pressure during each operation of the in-- 'terrupter to release the pressure Within said chamber and thereby produce a change of state from the superheated to the saturated vapor condition in the iiuid surrounding the arc, said predetermined pressure being in the region on the temperature-pressure curve for an adiabatic expansion of said fluid where the rate or" change of temperature with respect to pressure is high, said chamber and said pressure maintaining means being so proportioned that the coo g resulting from the pressure releasing operation causes the entrapped fluid adjacent the arc path to remain in the saturated vapor condition for a period of time at least equal to one alternation of the arc current.

5. In a circuit interrupter, a closed arc extinguishing chamber, means for causing an arc in said chamber, and liquid means within said chamber which when acted upon by the arc gives off a gas substantially all of which is condensable, said liquid means only partially filling said closed chamber, the space above the level of said liquid being utilized for accumulating the gas liberated by the action of the arc, said are extinguishing chamber being of substantially constant volume at all times and having a pressure release member biased to the closed position associated therewith, said pressure release member being operable, durlng each operation of said interrupter, to open said closed chamber at a predetermined pressure and thereby produce a change of state from the superheated to the saturated vapor condition in the fluid surrounding the arc, said chamber and said pressure maintaining means being so proportioned that the cooling resulting from the pressure releasing operation causes the entrapped fiuid adjacent the arc path to remain in the saturated vapor condition for a period of time at least equal to one alternation of the arc I current.

6. In a circuit interrupter, a closed are extinguishing chamber, means for causing an arc in said chamber, and liquid means within said chamber which when acted upon by the arc gives off a gas substantially all of which is condensable, said liquid means only partially filling said closed chamber, the space above the level of said liquid bein utilized for accumulating the gas liberated by the action of the arc, said are extinguishing chamber being of substantially constant volume at all times having a pres sure release member biased to the closed position associated therewith, said pressure release member being operable, during each operation I of said interrupter, to open closed chamber at a predetermined pressure and thereby produce a change of state from the superheated to the saturated vapor condition in the fluid surrounding the are, said predetermined pressure being in the region on the temperature-pressure curve for an adiabatic expansion of said fluid where the rate of change temperature with respect to pressure is high, said chamber and said pressure maintaining means being so proportioned that the cooling resulting from the pressure releasing operation causes the entrapped fluid adjacent the arc to remain in the saturated vapor condition for a period of time at least equal to one alternation of the arc current.

'7. In combination, a pair of relatively movable contact members for opening and closing the circuit, a closed pressure chamber for enclosing said relatively movable contact members during the opening of the connected circuit, releasable means for maintaining pressure within said closed chamber, and magnetic means responsive to the current in the connected circuit for biasing said pressure maintaining means to the closed position.

8. In an alternating current circuit interrupter, means for causing an are, means including a vaporizable fluid disposed along the path of said are for evolving a condensable gas when acted upon by the are, means for retaining said gas at substantially constant volume, adjacent the arc, and cooling means operable in response to the pressure of said gas, for causing the gas retained adjacent the arc to condense along the arc path, the means for retaining said gas, the pressure at which said cooling means operates, and the rate of removal of heat by said cooling means being so adjusted with respect to each other that the condensing operation is caused to persist for a sufficient period of time to include at least one zero point in the arc current.

9. In an alternating current circuit interrupter, means defining a chamber that is substantially closed when said interrupter is in the closed circuit position, means for drawing an arc in said chamber, said chamber containing a quantity of liquid, a portion of which is adapted to be gasifled by the arc, said gasified portion being at least partially condensable when cooled, and means operable during each circuit interrupting operation, in response to the pressure within said chamber, to cool the entrapped gaseous fluid adjacent the are, thereby effecting a change of state in said fluid from the superheated to the saturated vapor condition, said chamber, the pressure at which said cooling means operates, and the rate of removal of heat by said cooling means being so adjusted, with respect to each other, that said cooling and the resulting change of state is caused to persist for a sufiicient period of time to include at least one zero point in the arc current.

10. In an alternating current circuit interrupter, m ans defining an expansion chamber that is substantially closed when said interrupter is in the closed circuit position, means for drawing an arc in said chamber, said chamber containing a quantity of a liquid, a portion of which is adapted to be gasified by the arc to produce a gas substantially all of which is inorganic in nature, said gasified portion being at least partially condensable when cooled, and means operable durlng each circuit interrupting operatio in response to the pressure within said chamber, for effecting a substantially adiabatic expansion of said gasified portion in order to cool the entrapped gaseous fluid adjacent the said cooling causing at least a portion of said gas adjacent the arc to change from the superheated to the saturated vapor condition, said chamber and said expansion means being so proportioned with respect to the pressure at which said expansion means operates that said cooling and the resulting change of state in the fluid surrounding the arc is made to persist for a period of time at least equal to one alternation of the arc current.

11. In an alternating current circuit interrupter, means defining a chamber that is sub stantially closed when said interrupter is in the closed circuit position, means for drawing an arc in said chamber, said chamber containing a quantity of liquid, a portion of which is adapted to be gasified by the arc, said gasified por tion being at least partially condensable when cooled, and means operable during each circuit interrupting operation, in response to the pressure within said chamber to vent said chamber and to thereby cool the entrapped gaseous fluid adjacent the arc to effect a change of state in said fluid from the superheated to the saturated vapor condition, said chamber and said venting means being so proportioned with respect to the pressure at which said venting means operates that said cooling and the change of state produced thereby is caused to persist for a suificient period of time to include at least one zero point in the arc current.

12. The method of extinguishing an alternating current are which includes the steps of drawing an arc, gasif'ying' a quantity of a; substance, which liberates a condensable gas, by the heat of the arc, confining the gas and the arc to effeet a superheating of the gas and thereby increasing its pressure until a predetermined value is reached, and then substantially adiabatically expanding at least a portion of the superheated gas in such manner that the rate of heat removal shall cause the gas confined adjacent the arc to change from the superheated to the saturated vapor condition and to remain in the saturated vapor condition for a period of time at least equal to one alternation of the arc current.

FRITZ KESSELRING. 

